Electroplating reactor including back-side electrical contact apparatus

ABSTRACT

An apparatus for electroplating a workpiece is disclosed in which the apparatus includes a workpiece holding structure. The workpiece holding structure includes a workpiece support having at least one surface that is disposed to engage a front side of the workpiece and at least one electrical contact disposed for contact with at least one corresponding electrical contact on a back-side of the workpiece. The workpiece includes one or more electrically conductive paths between the at least one corresponding electrical contact and a front-side of the workpiece to facilitate electroplating of the front-side surface. An actuator is provided for driving the workpiece support between a first position in which the at least one electrical contact of the workpiece and the at least one contact of the workpiece holding structure are disengaged from one another, and a second position in which the at least one surface clamps the workpiece in a position in which the at least one electrical contact of the workpiece holding structure electrically engages the at least one electrical contact of the workpiece.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 09/114,261, filedJul. 11, 1998 now U.S. Pat. No. 6,322,678.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

Microelectronic circuits use metallization for a wide range of purposes.For example, metallization may be used to electrically interconnect thevarious components on a workpiece, such as the components formed in asemiconductor wafer. Further, the metallization may be used to form theactual electronic components on the workpiece. Such components include,for example, read/write heads, waveguides, inductors, etc.

There are a wide range of manufacturing processes that may be used todeposit the metallization on the workpiece in the desired manner. Suchprocesses included chemical vapor deposition, physical vapor deposition,and electroplating. Of these, electroplating is often preferable sincethe capital and the operating costs of electroplating are generally lessthan other metallization processes. Electroplating can take place atambient temperatures and ambient pressures. As such, strict control ofthe ambient temperature and pressure conditions is unnecessary.

Electroplating of workpieces that are used to form microelectroniccircuits generally takes place in a reactor. One such reactor isillustrated generally at 2 of FIG. 1 and is described in more detailedin U.S. Ser. No. 08/988,333 filed Sep. 30, 1997 entitled “SemiconductorPlating System Workpiece Support Having Workpiece—Engaging ElectrodesWith Distal Contact Part and Dielectric Cover”, the teachings of whichare hereby incorporated by reference. As shown in FIG. 1, the reactor 2generally comprises a rotor head 3 that supports the workpiece 4 so thatthe side of the workpiece to be processed (front side) is disposed tocontact the upper surface of a plating bath 5 that is held in areservoir 6 or the like. In this position, only the front side of theworkpiece 4 contacts the plating bath 5 while the back side (side of theworkpiece that is not to be processed at that time) preferably does notcontact the plating bath. An anode assembly 7 is disposed in the platingbath 5 and is connected to a positive potential terminal of a platingpower supply 8. A plurality of finger contacts 9 or the like contact thefront side of the workpiece 4 and serve to electrically connect theworkpiece 4 to a negative potential terminal of the plating power supply8. In operation, the plating power supply provides an electricalpotential difference between the anode and the workpiece which resultsin a chemical plating reaction at the front side of the workpiece inwhich the desired metal is deposited.

Although the foregoing reactor construction is suitable for manymicroelectronic electroplating applications, the present inventors haverecognized that such a construction may be a disadvantage in otherapplications. These disadvantages are generally associated with thefinger contacts. To electroplate a workpiece, electrical contact must bemade with the surface of the workpiece to be plated. Usually only theactive, front side of the workpiece is electrically conductive, and itis this surface to which electrical contact is made. Consequently, whenthe workpiece 4 is disposed so that it is in contact with the platingbath, the finger contacts 9 are also submerged in the plating bath. Assuch, the finger contacts 9 must be constructed to withstand the wet andharsh conditions of the plating bath environment. Construction of suchcontacts can be quite costly. For example, to withstand the environment,the finger contacts 9 may be constructed so that they have a platinumcore that functions as the conductive portion of the finger, and anexterior skin that is comprised of titanium and a dielectric materialsuch as PVDF. Even when such costly materials are used, the contacts maynot be completely resistant to degrading in the plating bath. If thefinger contacts are unable to withstand the plating bath environmentover time, they will gradually degrade and become ineffective asconductive contacts. Further, such degradation may result in theintroduction of contaminants into the plating bath, even before contactdegradation is visibly apparent.

Other problems are also associated with this front side contactgeometry. Making electrical contact to the front side of the workpieceusually involves complicated mechanisms which negatively impactreliability of the overall apparatus. A further potential problemresults from the fact that plating takes place at an accelerated rateproximate the finger contacts. This accelerated deposition results innon-uniformly of the metallization as measured across the entire surfaceof the workpiece. As the microelectronics industry drives toward furtherminiaturization of microelectronic devices, such non-uniformities cannotbe tolerated.

The present inventors have thus recognized that it would be advantageousin certain processes to provide an apparatus for electroplating aworkpiece which reliably makes electrical contact to a back side (sidenot then in-process at the processing station) of the workpiece yet canelectroplate the front side. The present inventors have also recognizedthat it would be advantageous to provide a back side contact which wouldsimplify part design, reduce material costs, and improve apparatusreliability.

BRIEF SUMMARY OF THE INVENTION

An apparatus for electroplating a workpiece is disclosed in which theapparatus includes a workpiece holding structure. The workpiece holdingstructure includes a workpiece support having at least one surface thatis disposed to engage a front side of the workpiece and at least oneelectrical contact disposed for contact with at least one correspondingelectrical contact on a back-side of the workpiece. The workpieceincludes one or more electrically conductive paths between the at leastone corresponding electrical contact and a front-side of the workpieceto facilitate electroplating of the front-side surface. An actuator isprovided for driving the workpiece support between a first position inwhich the at least one electrical contact of the workpiece and the atleast one contact of the workpiece holding structure are disengaged fromone another, and a second position in which the at least one surfaceclamps the workpiece in a position in which the at least one electricalcontact of the workpiece holding structure electrically engages the atleast one electrical contact of the workpiece.

In accordance with one embodiment of the present invention, theworkpiece holding structure includes a workpiece support member havingfingers for engaging a front side of the workpiece, and back-sidecontact device that includes at least one electrical contact arranged toface a back side of the workpiece. One or more actuators drive theworkpiece support toward the electrical contact to hold the workpieceresiliently clamped between the electrical contact and the fingers.

Numerous advantages and features of the present invention will becomereadily apparent from the following detailed description of theinvention and the embodiments thereof, from the claims and from theaccompanying drawings in which details of the invention are fully andcompletely disclosed as part of this specification.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic illustration of an electroplating reactor system.

FIG. 2 is a partial sectional view of one embodiment of anelectroplating reactor system that may incorporate the presentinvention.

FIG. 3 is a sectional view of one embodiment of a processing head thatmay be used in the reactor system of FIG. 2.

FIG. 4 is a perspective view of the processing head of FIG. 3.

FIG. 5 is an exploded perspective view of a workpiece rotor assemblyconstructed in accordance with one embodiment of the present invention.

FIG. 6 is a cross-sectional view of the workpiece rotor assembly of FIG.5 after it has been assembled.

FIGS. 7 and 8 are perspective views of the workpiece rotor assembly.

FIG. 9 is and exploded view of the components of one embodiment of aback-side contact device.

FIGS. 10 and 11 are perspective views of the back-side contact device ofFIG. 9 after it has been assembled.

FIGS. 12-14 illustrate a workpiece support assembly constructed inaccordance with one embodiment of the invention.

FIGS. 15A-15F illustrate the disclosed workpiece rotor assembly duringloading and unloading of the workpiece.

FIGS. 16A-16D are sectional views of the workpiece rotor assembly atvarious operational states illustrated in FIGS. 15A-15F.

FIGS. 17A and 17B illustrate to exemplary manners for providing aconductive path between the back-side of the workpiece and thefront-side of the workpiece.

DETAILED DESCRIPTION OF THE INVENTION

While this invention is susceptible of embodiment in many differentforms, there are shown in the drawings and will be described herein indetail specific embodiments thereof with the understanding that thepresent disclosure is to be considered as an exemplification of theprinciples of the invention and is not intended to limit the inventionto the specific embodiments illustrated.

FIG. 2 illustrates a reactor 10 in accordance with one embodiment of thepresent invention. Generally stated, the reactor comprises a processinghead 12 and an electroplating bowl assembly 14. In the disclosedembodiment, the processing head 12 accepts the workpiece for processing,introduces the workpiece to the bowl assembly 14 for processing, andremoves the workpiece from the bowl assembly 14 after processing fortransition to, for example, another processing station. Additionally,the processing head 12 includes the requisite electrical contacts toprovide electroplating power to the workpiece under process. Stillfurther, the processing head 12 may provide the capability of rotatingthe workpiece about axis R during, for example, processing of theworkpiece.

The processing head 12 of the illustrated embodiment includes a rotarydrive assembly 92 and a workpiece rotor assembly 100. The workpiecerotor assembly 100 is constructed to support and hold a workpiece, suchas a semiconductor, glass, or ceramic-based workpiece, duringprocessing. Further, assembly 100 includes components that provideelectrical plating power to the back-side of the workpiece. Theworkpiece rotor assembly 100 of the disclosed embodiment cooperates withthe rotary drive assembly 92 to rotate the workpiece about spin axis Rduring processing.

FIGS. 2 and 3 illustrate one embodiment of the rotor drive assembly 92.As illustrated, the rotor drive assembly 92 accepts a shaft 150 of theworkpiece rotor assembly 100 which is driven by a rotary motor 151 torotate the workpiece rotor assembly 100 about axis R.

The rotor drive assembly 92 also includes one or more components thatare used to drive one or more corresponding components in the workpiecerotor assembly 100 to cause such corresponding components to engage anddisengage from the workpiece. In the illustrated embodiment, suchfunctions are performed by a plurality of linear pneumatic actuators 94a, 94 b, 94 c that are fixed to a base plate 95. Each of the actuators94 a, 94 b, 94 c includes a respective piston rod, such as at 96 of FIG.3, that is connected to a thrust ring 98 by a securement 97. Actuationand de-actuation of the actuators 94 a, 94 b, and 94 c drives therespective piston rods to urge the thrust ring 98 in the directionsindicated by arrow 102. This causes the thrust ring 98 to engage anddisengage from corresponding components in the workpiece rotor assembly100. A more detailed description of this co-operation will be set forthbelow. Other means for providing such engagement and/or disengagementfrom the corresponding components in the workpiece rotor assembly 100are likewise suitable for use.

Electroplating power is provided to the rotor assembly 100 forapplication to the workpiece during processing. If, as in the disclosedembodiment, the rotor assembly 100 is disposed to rotate the workpieceduring processing, a substantially continuous electrical contact shouldbe made between the rotor assembly 100 and the source of plating powerduring the rotation. To this end, a conductive rotary connection, showngenerally at 215, is provided at an end of shaft 150. The rotaryconnection 215 is comprised of a stator contact 216 and a rotor contact217. The stator contact 216 is connected to receive power from aterminal of a plating power supply (not shown). The rotor contact 217 iselectrically connected to one or more components of the rotor assembly100 that provide plating power to the workpiece. During rotation of therotor assembly 100, the rotor contact 217 engages a conductive surfaceof the stator contact 216 to complete an electrical connection betweenthe terminal of the plating power supply and the workpiece, Since theconductive surface of the stator contact 260 is continuous about thetravel path of the rotor contact 217, the electrical connection betweenthe plating power supply and the workpiece is maintained throughout therotation of the rotor assembly 100.

FIGS. 5 through 8 illustrate one embodiment of the workpiece rotorassembly 100. Generally stated, the workpiece rotor assembly 100 iscomprised of a back-side contact device 107, a workpiece support 120,one or more components used to provide relative movement between thecontact device 107 and the workpiece support 120, and one or morecomponents used to interconnect the rotor assembly 100 with the rotarydrive assembly 92. Optionally, the rotor assembly 100 may include one ormore current thieves, such as the one shown at 110 of FIG. 5.

In the illustrated embodiment, the rotor assembly 100 includes an innerhub portion 103 that is mounted within an outer hub portion 104 by aplurality of fasteners 105. The back-side contact device 107 is centeredon and mounted to the outer hub portion 104 by a plurality ofnon-conducting securements 109 that proceed through securement apertures111 and into corresponding threaded bores 112 of the outer hub portion104.

The back-side contact device 107 of the disclosed embodiment includes adisc shaped hub block 203 formed from a dielectric material. Withreference to FIGS. 9-11, the hub block 203 includes one or more openings220 a-220 d through which one or more contacts 154 a-154 d extend tocontact corresponding conductive surfaces formed on a back-side of theworkpiece that is under process. As best seen in FIG. 11, an annulargroove 196 is disposed in the face of the block 203 and is dimensionedto receive a resilient O-ring 198. The O-ring 198 is disposed to engagethe back-side of the workpiece under process to thereby isolate andprotect the contacts 154 a-154 d from the plating environment.

In the disclosed embodiment, the contacts 154 a, 154 b, 154 c, 154 d areformed as upstanding members that extend from corresponding arms of aconductive cross-shaped member 204. The crossshaped member 204 isrecessed into a corresponding cross-shaped recess 226 formed in the rearsurface 228 of the block 203. The contacts 154 a, 154 b, 154 c, 154 dextend through openings 220 a, 220 b, 220 c, 220 d, and beyond surface229 of the hub block 203. The arms of the cross-shaped member 204 arethin so as to form individual cantilever leaf springs that allow them toresiliently deform when the contacts 154 a-154 d engage the workpiece.Thus the contacts can individually conform to the surface of theworkpiece W while ensuring copper electrical contact with the workpiece.Additionally, as the contacts are pushed against the workpiece, a slightscraping motion results from the leaf spring action. This scrapingmotion assists the contacts in penetrating any oxide film or othercontaminants on the back-side of the workpiece to thereby improveelectrical contact to the workpiece.

The cross-shaped member 204 is secured to the block 203 with aconductive electrode contact 208. The electrode contact 208 includes athreaded barrel portion 210 that terminates at a male contact element orplug 212. The threaded barrel portion 210 extends through a centralaperture of the cross-shaped member and secures with a correspondingthreaded aperture 240 that is disposed at a central portion of the hubblock 203. When thus secured, the cross-shaped member 204 is heldagainst hub block 203 by a square flange portion 216 of the contact 208.Flange portion 216 is preferably a standard dimension to accommodate atool, such as a wrench, to facilitate assembly.

As illustrated in FIG. 9, a central, annular groove 230 is disposed inthe rear surface 228 of the block 203 and is generally concentric withthreaded aperture 240. A resilient O-ring 234 is disposed in the groove230 and seals against an underside of the cross-shaped member 204. TheO-ring assists in isolating the plug 208 and associated conductor 214from the process chemistry.

As illustrated in FIG. 6, the plug 212 is connected to a correspondingsocket 213 that is formed on a metallic conductor rod 214 or otherelectrical conductor. The rod 214 provides an electrically conductivepath between the plug 212 and the rotor contact 217. The conductor rod214 includes a shoulder 218 which overlies a retaining ring 219 which isbacked by a shoulder 217 of the shaft 150. This configuration holds thesocket stationary while the plug 212 is inserted during attachment ofthe back-side contact device 107 to the outer hub portion 104.

As illustrated in FIG. 7 the protruding contact 208 is presented, raisedfrom the rear surface 228, to be received in the socket 213. The plug isinserted into the socket 213 as the hub block 203 is fastened onto theouter hub portion 104 by the securements 109. This causes the plugportion 212 to be resiliently captured within socket 213. When engagedin this manner, an O-ring 144 is held by the back-side contact place 107within a corresponding groove 146 to seal a central region of theback-side contact device 107 against the outer hub portion 104. Thisarrangement assists in sealing the contact 208 from process chemistry.

With reference again to FIGS. 5-8, the rotor assembly 100 includes theworkpiece support 120 which is mounted for relative movement withrespect to the back-side contact device 107. In the illustratedembodiment, the workpiece support 120 is designed to accommodate asubstantially square workpiece for processing. However, it will berecognized that other workpiece shapes may be accommodated with minormodifications to the workpiece support.

When designed for the processing of substantially square workpieces, theworkpiece support 120 preferably has a square shape having asubstantially square open central region 122 which is sized to begreater than the outside diameter of the back-side contact device 107.The workpiece support 120 also includes vertically arranged actuatorshafts 126, 128 which penetrate apertures 132, 134 of the outer hubportion 104 and are fastened to bias members 108 which draw theworkpiece support 120 toward the outer hub portion 104. The bias members108 are disposed for contact by corresponding components in the rotorhead assembly 92 that are used to drive the workpiece support 120 awayfrom outer hub portion 104 to, for example, accept a workpiece that isto be processed.

In the illustrated embodiment, the bias members 108 are in the form ofspring actuators that proceed through apertures 160 tormed in radialspokes 161 of the inner hub portion 103 and are secured to the outer hubportion 104 by fasteners 104 b. Each actuator includes a coil spring 114held partially within a cylindrical housing 116 and backed and retainedby a spring cap 118. Actuator shafts 126 and 128 are fixed to the springcaps 118 by respective securements 135. Spring expansion force againstthe spring caps 118 draws the actuator shafts 126, 128, and theworkpiece support 120, toward the outer hub portion 104.

FIGS. 12-14 illustrate the workpiece support 120 in more detail. Asshown, the workpiece support 120 includes a rectangular frame member 260which, for example, can be formed of stainless steel. Fit onto the framemember 260 are first and second rails 262, 264 which each include anouter plate 266 aid an overlying platform 268. The rails 262, 264 arepreferably formed from a dielectric material.

The fingers 152 a, 152 b are preferably formed integrally with the firstrail 262 and the fingers 152 c, 152 d are preferably formed intergrallywith the second rail. The fingers are also preferably formed from of adielectric material. The fingers each include a vertical leg 155 and anoverhang portion 157. Each of the vertical legs 155 includes a guidesurface 156. On two sides of the frame are located upstanding lead-inpins 153 a, 153 b which precisely locate the workpiece on the frame inconjunction with the guide surfaces 156 of vertical legs 155.

The first and second rails are each fastened to the rectangular frame260 by two countersunk fasteners 266 (see FIG. 14) which are screwedinto holes 270 in the frame member 260. The actuator shafts 126, 128penetrate through oval holes 276, 278 in the frame member 260.

The actuator shafts 126, 128 each have a cross pin 274 connection asshown in FIG. 14. The cross pins 274 are captured between the respectiverails 262, 264 and the frame member 260 by fasteners 266. The first rail262 includes a triangular guide channel 280 for precisely laterallylocating and restraining the cross pin 274 of the first actuator shaft126, while the second rail 274 includes a rectangular void 282 whichallows lateral movement of the second actuator shaft 128. A blind hole281 intersects the triangular guide channel 280 in the first rail, andloosely receives a top end 282 of the shaft 126. The triangular guidechannel 280 captures the pin 274 on either side of the blind hole 281.The oval holes 276, 278 allow some lateral movements (left and right inthe plane of FIG. 13 of the actuator shafts 126, 128) while restrictingmovement transverse thereto (into the plane of FIG. 13). Thus, thelateral position of the frame 260 is set by the first actuator shaft 126while the second actuator shaft 128 can laterally float. This preventsbinding of the tray during operation, due to misalignment ormisadjustments.

As noted above, the workpiece rotor assembly 100 may employ one or morecurrent thieves. In the illustrated embodiment, a single current thief110 is used. The current thief 110 is formed as a conductive platehaving a generally circular perimeter and a centrally disposed openingthat is shaped and dimensioned to expose the workpiece to the platingsolution.

The optional current thief 110 is supported by a plurality of dielectricstandoffs 105. The standoffs 105 are preferably fastened to the outerhub portion 104 by electrically conducting studs 106 which extendsthrough the standoffs 105 and the inner hub portion 103 to ultimatelyterminate at an electrical connection for the current thief 110. The hubportions 103, 104 and standoffs are composed of a dielectric material. Afurther embodiment of a current thief assembly suitable for use in thepresent invention is set forth in U.S. Ser. No. 08/933,450, filed Sep.18, 1997, and titled “Cathode Current Control System For A WaferElectroplating Apparatus”, the teachings of which are herebyincorporated by reference.

FIGS. 15A through 15F illustrate operation of the processing head 12during workpiece loading and unloading. FIGS. 16A through 16D illustratethe cooperation between the workpiece W and workpiece rotor assembly 100at various operational steps corresponding to FIGS. 15A through 15F.

FIG. 15A illustrates the workpiece support 120 in a rest state. In thisstate, the workpiece support 120 is pulled toward outer hub member 104by actuators 108.

FIGS. 15B and 16A show the workpiece rotor assembly 100 in a state inwhich it is ready to receive workpiece W. In this state, the wafersupport 120 is driven to a position above a surface of the thief 110thereby making it ready to receive the workpiece W from an end effector170 of an automation robot (not shown). In the illustrated embodiment,the workpiece support 120 is driven to this position when the actuators94 a, 94 b, 94 c drive the thrust ring 98 against the spring caps 118(see FIG. 6). This applies a compressive force to actuators 108 andurges the actuator shafts 126 and 128 and the arrest of the wafersupport assembly away from the surface of the outer hub portion 104.FIG. 16A illustrates the workpiece support 120 in this elevatedposition. In the position illustrated in FIG. 16A, the shoulders 180 areraised above the contacts, such as the contact 154 a shown.

FIGS. 15C and 16B illustrate delivery of the workpiece W onto theworkpiece support 120. Upon initial delivery, the workpiece W isdisposed beneath the overhang portions 157 of each finger 152 a, 152 b,152 c and 152 d, and above the lead-in pins 153 a, 153 b. The endeffector 170 includes a slot or notch 178 for avoiding the lead-in pin153 a thereby allowing the end effector to deposit and withdraw theworkpiece W without obstruction.

In FIGS. 15D and 16C, the end effector 170 has been withdrawn. Afterwithdrawal, the workpiece W is located between the lead-in pins 153 a,153 b and deposited onto shoulders 180 located beneath the overhangportions 157 of each finger 152 a, 152 b, 152 c, 152 d. To withdraw theend effector 170 (without also withdrawing the workpiece) the endeffector 170 and workpiece can be lowered until a trailing edge 182 ofthe workpiece abuts the lead-in pin 153 a, preventing the workpiece fromremaining on the end effector as the end effector is withdrawn. As theend effector 170 is lowered, the inclined guide surface 156 of eachvertical leg 155 of each of the fingers guides the lateral edges of theworkpiece W so that it is placed at the proper location on the workpiecesupport 120.

FIGS. 15E and 16D illustrate the manner in which the workpiece W isclamped by the workpiece support 120 against the back-side contactdevice 107 for processing. To effect this clamping, actuators 94 a, 94b, and 94 c are deactivated thereby causing thrust ring 98 to disengagefrom the spring caps of the actuators 108. This allows the actuators 108to return to their natural condition in which they drive the workpiecesupport 120 to clamp the workpiece W against the back-side contactdevice 107. In this position, the overhang portions 157 of the fingerscome into contact with a front side 186 of the workpiece, while theback-side 187 of the workpiece is resiliently supported on the contacts154 a, 154 b, 154 c, 154 d of contact device 107. In this position, theworkpiece also engages O-ring 198 to form a seal that protects thecontacts from exposure to the plating chemistry. Further, the shoulders180 lose contact with the workpiece W. The overhang portions 157 of thefingers come into pressing contact with the front side 186 of theworkpiece to hold the workpiece W against the contacts, such as thecontact 154 a illustrated. Because of the concave shape of each overhangportion 157, only an end 157 a is in contact with the front side 186 ofthe workpiece W. The edge 181 moves above the guide surface 156 and awayfrom the vertical legs 155. The lead-in pins, such as pin 153 aillustrated, drop to a position below the workpiece W. This preventsunwanted plating or wicking of process fluids on the edge 181 or backside of the workpiece W. The lead-in pins 153 a, 153 b are lowered withthe frame below a lead edge 184 and the trailing edge 182 of theworkpiece W.

After the workpiece W has been clamped against the back-side contactdevice 107, the processing head 12 can be driven to a position in whichit engages the electroplating bowl assembly 14 for processing of theworkpiece W. With reference to the specific embodiment of the reactorshown in FIG. 2, the processing head 12 mates with the processing bowlassembly 14 to form a substantially closed processing volume 13 duringworkpiece processing. As illustrated, the processing head 12 ispreferably supported by a head position controller 52. The head positioncontroller 52 of the disclosed embodiment includes a linear drive 53which is used to adjust the height of the processing head 12 withrespect to the bowl assembly 14. The head position controller 52 of thedisclosed embodiment also includes a head rotor drive 54 which operatesto rotate the processing head 12 about a horizontal axis 55. Therotational movement of the processing head 12 allows it to be placed ina first position (illustrated in FIGS. 15A-16D) for loading andunloading a workpiece and a second position shown in FIG. 2 in which thefront side of the workpiece is exposed for contact with the uppersurface of the plating solution in the bowl assembly 14. A variety ofdrives which provide linear and/or rotational drive movement aresuitable for use in the illustrated system. Although the disclosedembodiment illustrates a processing head 12 that rotates from the firstto the second position, the wafer rotor assembly 100 may be modified tomake such rotation unnecessary.

In operation, plating chemistry is provided to the cup through adelivery tube 44 and proceeds therefrom through fluid outlet openings56. The fluid then proceeds around anode 42 and through a perforateddiffusion plate 66. An upper edge of side wall 60 forms a weir whichlimits the level of process fluid within the cup. Excess solution poursover this wier and into the reservoir chamber 18. The spent liquid fromchamber 18 is preferably returned to a reservoir where it can be treatedwith additional plating chemicals and used again.

After processing is complete, the processing head 12 returns to thefirst position. In this position, actuators 94 a, 94 b, 94 c areactivated to drive the thrust ring 98 against the spring caps 118 (seeFIG. 7) and urge the workpiece support 120 to the position shown in FIG.15F. The end effector 170 can then be inserted beneath the workpiece Wto allow the end effector 170 to lift the workpiece above the lead-inpin 153 a. The workpiece is then withdrawn from the processing head 12in a reverse manner to its original insertion.

Because the vertical legs of the fingers and the lead-in geometryseparates from the workpiece in the final processing position, platingis prevented from occurring on the edge or back side of the workpiece.Only the front surface of the workpiece is substantially in contact withthe plating chemistry and there is no path for the plating chemistry towick to the edge or the back side of the workpiece.

The cantilever leaf spring design for the electrical contacts hasseveral advantages. The contacts and the common plate can be designedfrom a single piece of material, greatly simplifying part design andimproved reliability. Also, the contact design allows each contact to beresilient or compliant, ensuring sufficient contact is made by eachelectrical contact to the rigid surface defined by the back side of theworkpiece. Additionally, a distal end or contact point of each contactundergoes a slight “scraping” motion across the surface of the workpieceas it comes into contact with the workpiece as the contact leaf springdeflects. This scraping action is beneficial because it allows thecontact point to break through any oxide films or contaminants which mayinterfere with the quality of the electrical contact to the workpiecesurface.

FIGS. 17A and 17B illustrate to manners in which conductive contacts canbe formed on the back-side of the workpiece to conduct plating power tothe front-side thereof. In FIG. 17A, a plurality of conducting lines,such as at 400, are provided on the workpiece and proceed from theback-side to the front-side around the peripheral edge of the workpiece.In FIG. 17B, a plurality of conducting plugs, such as at 410, extendthrough the workpiece to connect metallization at the front-face of theworkpiece to contacts 415 on the back-side thereof.

Numerous modifications may be made to the foregoing system withoutdeparting from the basic teachings thereof. Although the presentinvention has been described in substantial detail with reference to oneor more specific embodiments, those of skill in the art will recognizethat changes may be made thereto without departing from the scope andspirit of the invention as set forth in the appended claims.

What is claimed is:
 1. An apparatus for use in a microelectronicworkpiece processing apparatus comprising: a drive plate connected forrotation by a drive apparatus; a hub carried on said drive plate andhaving an upper surface, said hub further having a plurality ofelectrical contacts extending resiliently above said upper surface; atray surrounding said hub, the tray having a first surface facingupwardly for supporting a microelectronic workpiece in a first stage ofoperation, and a second surface for holding said workpiece against saidcontacts in a second stage of operation; an automatic actuator connectedto provide relative motion between the tray and the hub to facilitateproper placement of the tray and the hub during the first and secondstages of operation.
 2. The apparatus of claim 1 wherein said secondsurface comprises a plurality fingers, each having a substantiallyvertical leg and an inwardly directed overhanging portion, said firstsurface comprising a shoulder arranged below each overhanging portion.3. The apparatus of claim 1 wherein a clearance between said first andsecond surfaces allow a transverse movement of the workpiece between thefirst and second surfaces.
 4. The apparatus of claim 1 wherein saidcontacts are carried on a common plate and said common plate is fastenedto said hub.
 5. The apparatus of claim 4 wherein said common plate isfastened to a backside of said hub and said hub includes apertures forreceiving said contacts from said common plate, and said contacts extendbeyond a front side of said hub.
 6. The apparatus of claim 5 whereinsaid common plate is cross-shaped and is fastened to said hub at acenter of said common plate.
 7. The apparatus of claim 4 wherein saidcommon plate is fastened by an electrode which also serves as electriccontact for said common plate.
 8. The apparatus of claim 1 wherein saidelectrical contacts are carried on leaf springs.
 9. The apparatus ofclaim 1 including an O-ring arranged around said contacts and sealsagainst said workpiece in the second stage of operation.
 10. Theapparatus of claim 1 wherein said first and second surfaces formopposing C-shaped channels that are dimensioned to allow side-loading ofthe workpiece onto the tray.